Table of contents

The idea of having this workshop in Madison was born at a table on the Terrace of the Union one evening in summer 2005. Francis Halzen, Albrecht Karle and I had just attended the first TeV meeting at Fermilab. We wished to convene the community of particle physicists and "new astronomers" who were using particles to study the universe, in order to hear about their activities and the methods they were using. All of us wanted this to be a meeting between both younger and more experienced people, and both experimentalists and theorists with a common background: dealing with signals produced in the universe that are not controlled by humans.

We decided to ask the organizers of the Fermilab workshop to have a second edition in Madison. The next edition is planned for summer 2007 in the Venice region of Italy. To make the meeting more productive, we planned to have a relevant number of working group sessions and open discussions chaired by invited conveners.

We singled out seven main areas for discussion at the Workshop with self-explaining names, calling the afternoon sessions Working Groups in those areas: 1) Gamma Astronomy, 2) Ultra-High-Energy Cosmic Rays, 3) Dark Matter, 4) Neutrino Astronomy, 5) New Technologies, 6) TeV Particle (i.e., connections between cosmic-ray, high-energy and accelerator physics) and 7) Gravitational Waves. The conveners had to not only organize the schedules, but also had the unfortunate task of summarizing all of the discussions which took place in their sessions for a presentation on the last day of the conference. Our web site ( http://www.icecube.wisc.edu/tev), developed by Rene Shei, allowed anybody to submit a proposal for a talk to the conveners of the appropriate Working Group(s). We felt that allowing this possibility provided an excellent chance for unknown young students to offer interesting proposals that could then be selected.

These Proceedings collect the work of a large number of experts and extremely active representative people from the various fields of Astroparticle Physics.

Acknowledgements

Due to the high quality of help that we received from them, we wish to acknowledge the conveners of the Working Groups mentioned in the text with the same numbering used above: 1) Felix Aharonian, Gus Sinnis, Frank Krennrich and Masahiro Teshima; 2) Piera Ghia and Tom Gaisser; 3) Laura Baudis and Gianfranco Bertone; 4) Lutz Koepke and Dan Hooper; 5) David Saltzberg and David Waters; 6) Ivone Albuquerque, Alexander Kusenko and Tom Weiler; and Bruce Allen and Guido Mueller. Special thanks also go to Tom Gaisser, who gave a comprehensive final summary of the conference. Throughout the Conference and the collection of these proceedings, Kim Kreiger constantly supported us. She was also responsible for the wonderful food available at coffee breaks and at the social dinner!

T Montaruli

The basic concept and the status of currently operating ground-based array detectors for VHE gamma-ray astronomy will be presented and compared with imaging air Cherenkov telescopes. Also an outlook of future prospects will be given.

Likely astrophysical sources of detectable high-energy (>>TeV) neutrinos are considered. Based on gamma-ray emission properties, the most probable sources of neutrinos are argued to be GRBs, blazars, microquasars, and supernova remnants. Di use neutrino sources are also briefly considered.

The controversial results of the cosmic ray energy spectrum at extremely-high energies (EHE) can be interpreted from the same source model(s) by taking into account rather large statistical and systematic errors of the present measurements. In addition we might have considered too simple pictures on possible EHE cosmic ray sources. Taking into account possible range of the extragalactic magnetic field configuration in clusters of galaxies, the source distribution in space, and primary particle emission intensities at each source leads to non-unique solutions of energy spectrum at earth, which makes it more difficult to resolve the long-standing mysteries on generation mechanism and sites that can produce a particle of such high energies. An alternative and complementary approach to study their origin is to explore EHE universe by penetrating neutral charge particles - neutrinos. What we can learn from measurements of EHE cosmic neutrinos are discussed. We finally present a detection possibility by the IceCube neutrino observatory.

We briefly discuss three aspects related to the origin of ultra-high energy cosmic rays (UHECRs) namely: 1) particle acceleration in astrophysical sources; 2) transition to an extragalactic origin; 3) spectrum and anisotropies at the highest energies.

Theoretical and experimental constructions together make a compelling case that the discovery of high-energy (≳10¹⁵eV) astrophysical neutrinos is imminent. In this talk, we investigate some of the reasons for excitement. We focus on the larger cosmic neutrino flux expected due to the recently-argued lower-energy cosmic-ray crossover from galactic to extragalactic origin; and on various aspects of source dynamics that can be probed by neutrino flavor physics. We conclude with a brief overview of the information contained in the fluctuations and correlations expected in neutrino flavor data.

VERITAS is a ground-based gamma-ray observatory covering energies between 100 GeV and 50 TeV and will start operating by January 2007. We give a brief report of the construction status and performance characteristics of the telescopes.

The status and future plans of the ongoing underwater neutrino telescopes projects ANTARES, BAIKAL, NEMO, NESTOR and KM3NeT are presented.

The IceCube neutrino telescope nears the end of its second running season having collected a sample of over 2 × 10⁹ triggered events. While the majority of these events are cosmic ray muons, the detector is already sufficiently well understood to allow identification of neutrinoinduced muon candidate events from the CR background. The production of optical module instrumentation is now well-established, the modules themselves are functioning properly with low failure rate, and it has been proven that the hot water drill can deliver the holes needed for deployment of these instruments. The project plans to deploy 12-14 strings each year during the next several austral summers to bring the detector volume to 1 km³.

An overview is presented of current worldwide activities in the field of the acoustic detection of ultra-high energy neutrinos. Emphasis is placed on recent results from test experimental setups, simulation work, sensitivity calculations and on data taken at deep-water deployments.

The Cryogenic Dark Matter Search (CDMS) and XENON experiments aim to directly detect dark matter in the form of weakly interacting massive particles (WIMPs) via their elastic scattering on the target nuclei. The experiments use different techniques to suppress background event rates to the minimum, and at the same time, to achieve a high WIMP detection rate. The operation of cryogenic Ge and Si crystals of the CDMS-II experiment in the Soudan mine has yielded the most stringent spin-independent WIMP-nucleon crosssection (∼ 10-43 cm²) at a WIMP mass of 60 GeV/c². The two-phase xenon detector of the XENON10 experiment is currently taking data in the Gran Sasso underground lab and promising preliminary results were recently reported. Both experiments are expected to increase their WIMP sensitivity by a one order of magnitude in the scheduled science runs for 2007.

Hadron production measurements for neutrino experiments is a well established field at CERN since the '70s. Precise prediction of atmospheric neutrino fluxes, characterization of accelerator neutrino beams, quantification of pion production and capture for neutrino factory designs, all of these would profit from hadron production measurements. In recent years, interest in such studies was revived and new generation of low-energy (from 3 to 400 GeV) hadron production experiments were built or proposed. Such experiments all share a basic design, consisting in the presence of open-geometry spectrometers, as close as possible to full angular coverage, and aiming at full particle identification. New results are now provided by Harp in the very low energy range (3 to 15 GeV/c) and by NA49 at 158 GeV/c. In the next years NA49- future will explore the medium energy range (30 to 400 GeV/c) and at LHC energies for the first time thanks to the TOTEM experiment, it will be possible to measure with unprecedented precision the total cross section beyond 1 TeV/c.

A unifying theme of this conference was the use of different approaches to understand astrophysical sources of energetic particles in the TeV range and above. In this summary I review how gamma-ray astronomy, neutrino astronomy and (to some extent) gravitational wave astronomy provide complementary avenues to understanding the origin and role of high-energy particles in energetic astrophysical sources.

TeV astronomy is currently dominated by Very High Energy¹ (VHE) γ-ray observations using a new generation of ground-based atmospheric Cherenkov telescopes. A few years of data taking with these instruments have yielded a spectacular view of the universe, probing some of the key science questions in high energy astrophysics today. TeV γ-ray observations may be pivotal in solving the question of the origin of cosmic rays, in understanding the physics of relativistic jets and their connection to black holes, may help us in disecting different contributions to the diffuse γ-ray emission from the galactic plane and provide prospects for astrophysical dark matter detection. The interpretation of extragalactic VHE γ-ray sources is complicated by appreciable absorption o. intergalactic diffuse radiation known as the Extragalactic Background Light (EBL). Attenuation features in TeV spectra of extraglactic sources due to the EBL provide an important link to optical/infrared astronomy and Cosmology.

VHE γ-ray astronomy is spearheading the TeV sky and has advanced our understanding of physical parameters in astrophysical sources at the highest energies through major improvements in the imaging capability and time resolved spectroscopy with the imaging atmospheric Cherenkov technique. Many aspects of the science questions addressed by TeV γ-ray observations will undoubtedly have consequences for neutrino astronomy in the next decade. This paper provides a brief summary of the scientific results and observations reported at the Working Group on Gamma Ray Astronomy at this conference.

This working group was mainly oriented to discuss experimental results on cosmic rays, from the lowest energies (obtained by direct measurements) up to the highest ones (obtained by extensive air shower indirect measurements). The theoretical contributions concerned the main problems of the modeling of cosmic ray interactions in the atmosphere and of cosmic ray acceleration at astrophysical shocks.

This working group focused mainly on the complementarity among particle physics and astrophysics. The analysis of data from both fields will better constrain theoretical models. Much of the discussion focused on detecting dark matter and susy particles, and on the potential of neutrino and gamma-ray astrophysics for seeking or constraining new physics.

The field of high-energy neutrino astronomy is rapidly developing. A number of new experiments are currently being deployed and developed. Additionally, the recent successes of TeV gamma-ray astronomy have exciting implications for future neutrino telescopes. Here we will summarize these and other issues as they were discussed in the TeV II workshop's neutrino astronomy working group.

Neutrino astronomy was initiated primarily to search for TeV to PeV neutrinos from Active Galactic Nuclei, and the optical Cherenkov technique is well suited for this energy range. Interest has grown recently in detecting EeV neutrinos, particularly the "cosmogenic" neutrinos produced during propagation of ultra-high-energy cosmic rays (UHECR) through the microwave background radiation. These neutrinos could be a powerful tool both to resolve the mystery of the UHECR sources and to test fundamental physics at the ∼100 TeV scale. The optical technique is not cost effective at these energies and newer techniques such as radio and acoustic detection are necessary. Accelerator experiments have con.rmed the production of both types of signals from high-energy showers in various media, and quantitative measurements have con.rmed theoretical descriptions of the signal strength, frequency content and pulse shape. While radio experiments have set the strongest limits so far, the acoustic method could contribute with an entirely independent signal production and detection mechanism and may be more effective at the highest energies. E.orts are underway to develop the acoustic method in various media around the world, with arrays operating in ocean water at the Bahamas, the UK, and the Mediterranean Sea; detectors prepared for deployment in the South Pole ice in the next year; and ideas for future acoustic detectors in salt domes and on Antarctica's Ross Ice Shelf. Regardless of which method is individually most sensitive, the best con.guration may be to co-deploy arrays to combine the techniques and seek coincident detection of individual neutrino events.

The Swift gamma-ray burst explorer was launched on Nov. 20, 2004 from Cape Canaveral, Florida. The .rst instrument onboard became fully operational less than a month later. Since that time the Burst Alert Telescope (BAT) on Swift has detected more than 180 gamma-ray bursts (GRBs), most of which have also been observed within two minutes by the Swift narrow-.eld instruments: the X-Ray Telescope (XRT) and the Ultra-Violet and Optical Telescope (UVOT). Swift trigger notices are distributed worldwide within seconds of the trigger through the Gamma-ray burst Coordinates Network (GCN) and a substantial fraction of GRBs have been followed up by ground and space-based telescopes, ranging in wavelength from radio to TeV. Correlations of Swift bursts with neutrino and gravity wave detectors have promise of finding the .rst non-electromagnetic signature of a GRB. Swift is also a sensitive X-ray observatory with capabilities to monitor galactic and extragalactic transients on a daily basis, carry out the .rst all-sky hard X-ray survey since HEAO-1, and study in detail the spectra of X-ray transients as part of coordinated multi-wavelength observing campaigns.

Gamma-ray bursts are the brightest transient sources of MeV γ-rays in the sky and are the leading candidate sources of the GZK cosmic rays. Physical conditions required to accelerate elementary particles to such high energies also, inevitably, lead to expected TeV energy γ-ray and neutrino emission from these sources. Although γ-rays of energy only up to 18 GeV have been detected from a few bursts, upcoming space- and ground-based detectors will probe these sources in the GeV-TeV energy range revealing their particle acceleration and emission mechanism(s) as well as constraining their astrophysical model(s).

The Gamma-ray Large Area Space Telescope (GLAST) is a space-based observatory scheduled to launch in October 2007 with two instruments: (1) the GLAST Burst Monitor (GBM), sensitive to photon energies between 8 keV and 25 MeV and optimized to detect gamma-ray bursts, and (2) the Large Area Telescope (LAT), sensitive to gamma rays between 20 MeV and 300 GeV and designed to survey the gamma-ray sky with unprecedented sensitivity. We describe the LAT and the GBM. We then focus on the LAT's capabilities for studying active galactic nuclei.

The H.E.S.S. (High Energy Stereoscopic System) experiment has been in operation in its current set-up since the beginning of 2004. The construction of the extension of H.E.S.S. ("Phase II") has started: A telescope with a mirror surface of 600 m2 in the center of the four existing H.E.S.S. Phase I telescopes This "Large Cherenkov Telescope" (LCT) will operate stand-alone as well as in coincidence together with the Phase I telescopes. The LCT will start triggering on gamma-ray initiated air showers at an energy of 20 GeV. In this contribution, a status of the existing installation and plan for the future will be given.

The diffuse gamma radiation arising from the interaction of cosmic ray particles with matter and radiation in the Galaxy is one of the few probes available to study the origin of the cosmic rays. Milagro is a water Cherenkov detector that continuously views the entire overhead sky. The large field-of-view combined with the long observation time makes Milagro the most sensitive instrument available for the study of large, low surface brightness sources such as the diffuse gamma radiation arising from interactions of cosmic radiation with interstellar matter. In this paper we report our results on diffuse emission from the galactic plane and in particular the Cygnus region. Our observations show at least one new TeV source MGRO J2020+37 as well as correlations with the matter density in the region as would be expected from cosmic-ray proton interactions. However, the TeV gamma-ray flux from the Cygnus region (after excluding MGRO J2020+37) is roughly 5 times that expected from a conventional model of cosmic ray production and propagation.

The field of Very High Energy (VHE) γ-ray emitting extragalactic sources has considerably evolved since the new generation of atmospheric Cerenkov telescopes (ACT) of improved sensitivity, such as H.E.S.S. array and the MAGIC ACT, have started operating. This has led to a wealth of new clues about emission mechanisms at high energy through the discovery of new sources, more accurate spectra and temporal studies of sources known previously, and simultaneous multi-wavelength (MWL) campaigns since broadband variability is a key phenomenon to the underlying physical mechanisms at play. The fact that some of these new sources are located at redshifts close to z ∼ 0.2 makes them powerful probes of the Extragalactic Background Light (EBL) through the attenuation of γ-rays above 100 GeV.

HAWC will have unprecedented sensitivity for a ground based particle detector array. It will be capable of observing the Crab at the 5σ level with each transit while simultaneously observing the entire northern sky (15 times the current Milagro detector sensitivity). The design an performance of the HAWC water Cherenkov gamma-ray observatory is presented.

The H.E.S.S. imaging air Cherenkov telescope array has performed a blind survey at energies above 100 GeV of parts of the Galactic plane as well as dedicated (deeper) observations of gamma-ray source candidates. New sources including shell type super-nova remnants, pulsar-wind nebulae, binary systems, cosmic ray illuminated molecular clouds, as well as unidentified sources have been found. In this contribution, a selected overview of the recent results focussing on shell type supernova remnants and pulsar wind nebulae is given.

With the recent successes of gamma-ray astronomy an obvious question is raised: where is this field going next? At present we have a network of similar air Cerenkov telescope arrays throughout the world and a large water detector in the USA. Here we try to identify which practical paths exist to newer, more sensitive instruments and what these might hold for the future.

An overview is presented of the scientific implications of direct measurements of cosmic rays in terms of the origins and history of these particles. Within the last several years important constraints have been placed on the possible origins of cosmic rays in the GeV energy range by the analysis of isotopic composition. At higher energies new magnet experiments to measure elemental composition have supported the notion that all nuclei should have similar behaviour with magnetic rigidity. At still higher energies, into the cosmic ray "knee", there are some disagreements between measurements, suggesting that there are various issues which remain to be resolved in this region. We also emphasize the important role played by measurements of spallation-produced nuclei in cosmic-rays. These hold the key to our understanding of cosmic ray source spectra at high energies.

Recent results of advanced experiments with sophisticated measurements of cosmic rays in the energy range of the so called knee at a few PeV indicate a distinct knee in the energy spectra of light primary cosmic rays and an increasing dominance of heavy ones towards higher energies. This leads to the expectation of knee-like features of the heavy primaries at around 100 PeV. To investigate in detail this energy region several new experiments are or will be devised.

A new method for making high-resolution ground-based measurements of the energy and charge of cosmic ray primaries in the region of the knee is presented. The method exploits the direct component of Cerenkov radiation emitted by cosmic ray nuclei prior to their first hadronic interaction in the atmosphere. A dedicated ground-based Direct Cerenkov detector could achieve model-independent charge and energy resolution as good as 15%, on an event-by-event basis.

The Pierre Auger Observatory was primarily designed for studying the energy region beyond 10¹⁹eV, but a significant aperture, and significant physics, is accessible at energies down to around 10¹⁸eV. In this paper we describe the physics studies planned for this region, including a description of the experimental techniques.

The High Resolution Fly's Eye (HiRes) experiment is a stereo air fluorescence detector for the study of cosmic rays with energies above 5×10¹⁷eV. Arrival directions of cosmic rays observed in stereo can be resolved with a typical uncertainty on the order of 0.5°, making the experiment ideal for small-scale anisotropy studies. Here we present the results of searches for correlation with astronomical sources, in particular the recently observed correlations with objects of the BL Lac subclass of active galaxies.

Interactions of energetic particles on target nuclei producing secondary particles from the Fermilab MIPP E907 experiment will be reviewed. Current simulation codes rely upon poorly measured results from the past. While current neutrino experiments, both atmospheric and accelerator based, rely upon MIPP and pion production measurements which are poorly known and dominate their errors. The goal for the current and future upgrade MIPP experiment is to dramatically improve these measurements. It is not only of interest to neutrino experiments, but also for designing hadronic calorimeters for the the International Linear Collider which must achieve unprecedented resolutions for reaching their stated physics goals.

The status of present theoretical description of very high energy hadronic interactions is reviewed. The impact of new results of accelerator and cosmic ray experiments on hadronic interaction model constructions is discussed in detail. Special attention is payed to remaining uncertainties in model extrapolations into the ultra-high energy domain, in particular, concerning model predictions for the muon component of extensive air showers. New promising theoretical approaches are outlined and future experimental prospects are discussed.

In R-parity conserving supersymmetric (SUSY) models the lightest SUSY particle (LSP) is stable and a candidate for dark matter. Depending on the coupling and mass of this particle the life time of the next-to-lightest SUSY particle (NLSP) may be large compared to experimental time scales. In particular, if the NLSP is a charged particle and its decay length is of the order of the Earth's diameter Cherenkov telescopes might observe parallel muon-like tracks of NLSP pairs produced in neutrino-nucleon interactions in the Earth's interior. We have investigated two SUSY scenarios with a long-lived NLSP and a gravitino LSP in view of the observability at the IceCube detector.

We study ultrahigh energy astrophysical neutrinos and their interactions. We find that for GZK neutrinos three flavor mixing is important and the neutrino flavor ratio at Earth deviates from 1:1:1. We show the effect of tau neutrino regeneration and tau energy loss as they propagate through the Earth. We also consider production of mini black holes, neutrino interactions via TeV string resonances and the supersymmetric charged sleptons (stau) production in neutrino interactions. We discuss signals for these processes in detectors such as Anita, EUSO and OWL.

The presence and growth of Intermediate and Supermassive Black Holes modify the surrounding distribution of stars and Dark Matter, and inevitably affect the prospects for indirectly detecting Dark Matter through its annihilation products. We show here that under specific circumstances, Black Holes can act as Dark Matter annihilation "boosters". In particular, we show that mini-spikes, i.e. Dark Matter overdensities around Intermediate-Mass Black Holes, would be bright sources of gamma-rays, well within the reach of the space telescope GLAST, that can be discriminated from ordinary astrophysical sources thanks to their peculiar energy spectrum and spatial distribution.

How large can the dark matter self-annihilation rate in the late universe be? This rate depends on (ρDM/m_χ)²⟨σA^v⟩, where ρDM/m_χ is the number density of dark matter, and the annihilation cross section is averaged over the velocity distribution. Since the clustering of dark matter is known, this amounts to asking how large the annihilation cross section can be. Kaplinghat, Knox, and Turner proposed that a very large annihilation cross section could turn a halo cusp into a core, improving agreement between simulations and observations; Hui showed that unitarity prohibits this for large dark matter masses. We show that if the annihilation products are Standard Model particles, even just neutrinos, the consequent fluxes are ruled out by orders of magnitude, even at small masses. Equivalently, to invoke such large annihilation cross sections, one must now require that essentially no Standard Model particles are produced.

We describe a new technique to look for evidence of the Higgs mechanism. The usual method involves seeking evidence for the Higgs boson either directly or via the indirect effect that a virtual Higgs boson would have on a variety of Standard Model parameters. The new technique looks for Higgs field effects that are predicted to reduce the masses of heavy particles when they are in the presence of other heavy particles.

Motivated by recent interest in TeV-scale gravity and especially by the possibility of fast baryon decay mediated by virtual black holes, we study another dangerous aspect of spacetime foam interactions: lepton flavor violation. We correlate existing limits on gravity- induced decoherence in the neutrino sector with a lower bound on the scale of quantum gravity, and find that if spacetime foam interactions do not allow an S-matrix description the UV cutoff is well beyond the electroweak scale. This suggests that string theory provides the appropriate framework for description of quantum gravity at the TeV-scale.

In astrophysical sources, TeV gamma-rays may originate by means of two wellknow mechanisms: via electromagnetic or hadronic processes. In this talk we discuss a third mechanism: the photodisintegration of nuclei at the source, followed by de-excitation of the daughter nuclei. We examine the conditions that need to be satisfied in the source so that a relevant contribution to the TeV gamma-ray flux may come from this mechanism and we also present the distinctive features of this dynamical framework, as is the absence of low energy counterparts. We also comment on the concomitant associated flux of antineutrinos coming from the β-decay of stripped neutrons, which turns out to be smaller than that of gamma-rays.

It is possible that TeV γ rays can originate in the photo-deexcitation of a PeV nucleus following photodisintegration via the Giant Dipole Resonance in an environment rich in Lyman alpha photons. This mechanism is examined as a candidate explanation of the recently discovered HEGRA source. The ultra-violet photon background results from the rich O and B star environment of the CygnusOB2 association. A signature of the mechanism is the existence of a lower limit ∼ 500 GeV on the γ-ray spectrum. The conditions for an measurable accompanying neutrino flux from neutron decay are assessed.

We discuss the interplay between electromagnetic energy loss and weak interactions in the context of quasistable particle particle propagation through materials. As specific examples, we consider staus, where weak interactions may play a role, and taus, where they don't.

One of the major goals of neutrino astronomy is to explore the otherwise unknown fluxes and interactions of ultrahigh energy neutrinos. The existing neutrino telescopes look at three types of events: particle showers, muons, and taus. In this paper we discuss the dependence of the event rates on the neutrino nucleon cross-sections as we scale the cross sections, with energy, in different scenarios beyond the standard model. Our focus will be on the IceCube detector.

In just the last few years, the catalog of known Galactic TeV gamma-ray sources has grown dramatically, due to the abilities of current air ¡Cerenkov telescopes to measure both the spectrum and morphology of the TeV emission. While these properties can be very well measured, they are not necessarily sufficient to determine whether the gamma rays are produced by leptonic or hadronic processes. However, if the gamma-ray emission is hadronic, there must be an accompanying flux of neutrinos, which can be determined from the observed gamma-ray spectrum. The upcoming km3 neutrino telescopes will allow for a direct test of the gammaray production mechanism and the possibility of examining the highest possible energies, with important consequences for our understanding of Galactic cosmic-ray production.

Loeb and Waxman have argued that high energy neutrinos from the decay of pions produced in interactions of cosmic rays with interstellar gas in starburst galaxies would be produced with a large enough flux to be observable. Here we obtain an upper limit to the diffuse neutrino flux from starburst galaxies which is a factor of ~5 lower than the flux which they predict. Compared with predicted fluxes from other extragalactic high energy neutrino sources, starburst neutrinos with ~ PeV energies would have a flux considerably below that predicted for AGN models. We also estimate an upper limit for the diffuse GeV γ-ray flux from starbust galaxies to be O(10-2) of the observed γ-ray background, much less than the component from unresolved blazars.

The Antarctic Muon And Neutrino Detector Array (AMANDA) is currently the most sensitive neutrino telescope at high energies. Data have been collected in a period of eight years and analyzed with different analysis strategies. Limits to the neutrino flux from point sources, transient emissions, source catalogs and limits to different diffuse flux models have been obtained implying in some cases strong constraints to hadronic interaction models of such sources. In this contribution, implications of the diffuse neutrino limit will be discussed with respect to neutrino production mechanisms in astrophysical sources.

In this paper we discuss the strategy developed in order to associate neutrinos with their cosmic sources using historical light curves. Periods of very intense photon activity are selected through a novel analysis approach. The statistical method called Maximum Likelihood Blocks is applied for the .rst time on light curves of high frequency blazars. In order to avoid any possible bias in the selection of periods with intense photon activity, the arrival time and incoming direction of the neutrinos are kept blinded. Following the approach here reported, neutrino fluxes below the atmospheric neutrino background level can become accessible. We report as well on a .rst step to establish a target-of-opportunity program based on neutrinos detected in IceCube which are used as alerting messenger particles.

Tau neutrino detection in IceCube would be strong evidence for the presence of cosmologically-produced neutrinos. In addition to the well-known "double bang" signature, we describe here five additional channels that we believe will not only extend the energy range over which IceCube can be sensitive to tau neutrinos, but also provide useful control over systematic uncertainties via self-consistency checks amongst all detection channels.

Kilometer-scale neutrino telescopes will detect muon and electron neutrinos from astrophysical sources at the TeV scale and above. Tau neutrinos are also expected from these sources due to neutrino oscillations over astrophysical baselines. Identification of tau neutrinos is expected to be possible above the PeV energy range through the "double bang" and "lollipop" signatures. We discuss another signature of tau in the PeV-EeV range, arising from the decay of tau leptons inside the detector to much brighter muons.

The status of the NEMO project is described: the activity on long term characterization of water optical and oceanographic parameters of the Capo Passero (Sicily, Italy), candidate for the installation of the Mediterranean km³ neutrino telescope; the feasibility study on physics performances and underwater technology for the km³; the activity on NEMO Phase 1, a technological demonstrator that is going to be deployed at 2000 m depth 20 km offshore Catania.

Results arc presented from the first ANTARES detector line, which has been operational since March 2006. The remaining 11 lines will be deployed in the course of the next 18 months. The first examples of reconstructed traversing muons are presented, as are the first results on the general detector performance.

Recent measurements of the energy spectra of Galactic TeV γ-ray sources with the H.E.S.S. instrument have been used to calculate the expected high energy neutrino fluxes from these sources. Based on the results the expected event rates in a next generation neutrino telescope in the Mediterranean Sea, KM3NeT, have been estimated, assuming an instrumented volume of 1 km³. We find that for energies above 1TeV event rates of a few neutrinos per year can be expected from the brightest γ-ray sources. Although these rates are comparable to those of the background from atmospheric neutrinos a detection of individual sources seems possible.

High-energy photons from pair annihilation of dark matter particles contribute to the cosmic gamma-ray background (CGB) observed in a wide energy range. The precise shape of the energy spectrum of CGB depends on the nature of dark matter particles. In order to discriminate between the signals from dark matter annihilation and other astrophysical sources, however, the information from the energy spectrum of CGB may not be sufficient. We show that dark matter annihilation not only contributes to the mean CGB intensity, but also produces a characteristic anisotropy, which provides a powerful tool for testing the origins of the observed CGB. We show that the expected sensitivity of future gamma-ray detectors such as GLAST should allow us to measure the angular power spectrum of CGB anisotropy, if dark matter particles are supersymmetric neutralinos and they account for most of the observed mean intensity. As the intensity of photons from annihilation is proportional to the density squared, we show that the predicted shape of the angular power spectrum of gamma rays from dark matter annihilation is different from that due to other astrophysical sources such as blazars, whose intensity is linearly proportional to density. Therefore, the angular power spectrum of the CGB provides a "smoking-gun" signature of gamma rays from dark matter annihilation.

A way to search for dark matter is to look for an excess in the cosmic positron spectrum above 1 GeV. In that context, an enhancement of the signal due to dark matter substructures is often introduced and referred to as the boost (or clumpiness) factor. Recent studies show not only that the boost factor does depend on energy, but is a statistical property of the distribution of substructures inside the Milky Way. Bertone's scenarios in which a relatively small number of intermediate-mass black holes are present in our Galaxy are investigated here. For m_χ = 100 GeV, boosts of order 10³ are found, with a high dispersion, especially near the source energy.

The intense 0.511 MeV gamma-ray line emission from the Galactic Center observed by INTEGRAL requires a large annihilation rate of nonrelativistic positrons. The emission is strongly concentrated at the Galactic Center (GC), in contrast to gamma-ray maps tracing nucleosynthesis (e.g., the 1.809 MeV line from decaying ²⁶Al) or cosmic ray processes (e.g., the 1-30 MeV continuum), which reveal a bright disk with a much less prominent central region. If positrons are generated at relativistic energies, higher-energy gamma rays will also be produced from inflight annihilation of positrons on ambient electrons. The comparison of the gamma-ray spectrum from inflight annihilation to the observed diffuse Galactic gamma-ray data constrains the injection energies of Galactic positrons to be less than 3 MeV.

We outline the WIMP dark matter parameter space in the Constrained MSSM by performing a comprehensive statistical analysis that compares with experimental data predicted superpartner masses and other collider observables as well as a cold dark matter abundance. We find that 10.10 pb≲SI p≲10⁻⁸ pb for direct WIMP detection (with details slightly dependent on the assumptions made). We conclude that most of the 95% probability region for the cross section will be explored by future one-tonne detectors, that will therefore cover most of the currently favoured region of parameter space.

The Dark Matter part of the universe presumably consists of WIMPs (Weakly Interacting Massive Particles). The ArDM project aims at measuring signals induced by WIMPs in a liquid argon detector. A 1-ton prototype is currently developed with the goal of demonstrating the feasibility of such a direct detection experiment with large target mass. The technical design of the detector aims at independently measuring the scintillation light and the ionization charge originating from an interaction of a WIMP with an argon nucleus. The principle of the experiment and the conceptual design of the detector are described.

By being the first observatory to survey the source rich low frequency region of the gravitational wave spectrum, the Laser Interferometer Space Antenna (LISA) will revolutionize our understanding of the Cosmos. For the first time we will be able to detect the gravitational radiation from millions of galactic binaries, the coalescence of two massive black holes, and the inspirals of compact objects into massive black holes. The signals from multiple sources in each class, and possibly others as well, will be simultaneously present in the data. To achieve the enormous scientific return possible with LISA, sophisticated data analysis techniques must be developed which can mine the complex data in an effort to isolate and characterize individual signals. This proceedings paper very briefly summarizes the challenges associated with analyzing the LISA data, the current state of affairs, and the necessary next steps to move forward in addressing the imminent challenges.

We review state of the art of the gravitational reference sensor (GRS) for the Laser Interferometer Space Antenna (LISA). LISA consists of three identical spacecraft placed at the corners of an equilateral triangle with a 5 million kilometer baseline. In the LISA baseline design, the spacecraft at each corner will have two optical assemblies subtending an angle of 60 degrees. A proof mass (PM) is housed in a GRS located at the center of each assembly. LISA measures the distance variation between PMs separated by 5 million kilometers to a precision of 40 pm/Hz^1/2. The GRS must shield the PM from external disturbances such as solar wind and functions as a drag-free sensor for spacecraft control. The GRS must minimize the back action and cross talk exerted by measurements themselves. Significant progress has been made in the design, fabrication and testing of the GRS. LISA Pathfinder will fly a test GRS system scheduled around 2009. In addition, there have also been new architectures proposed to simplify the LISA payloads by using a single PM and therefore only one GRS per spacecraft. Further a modular GRS (MGRS) structure is proposed to reduce complexity. Optical sensing and large gap size between the PM and the MGRS housing are proposed to lower the disturbance level. Many experimental, engineering design, and trade off studies are underway.

The ARIANNA concept utilizes the Ross Ice Shelf near the coast of Antarctica to increase the sensitivity to cosmogenic neutrinos by roughly an order of magnitude when compared to the sensitivity of existing detectors and those under construction. Therefore, ARIANNA can test a wide variety of scenarios for GZK neutrino production, and probe for physics beyond the standard model by measuring the neutrino cross-section at center of momentum energies near 100 TeV. ARIANNA capitalizes on several remarkable properties of the Ross Ice Shelf: shelf ice is relatively transparent to electromagnetic radiation at radio frequencies and the water-ice boundary below the shelf creates a good mirror to reflect radio signals from neutrino interactions in any downward direction. The high sensitivity results from nearly six months of continuous operation, low energy threshold (∼3x10¹⁷ eV), and more than 2π of sky coverage. The baseline concept for ARIANNA consists of moderately high gain antenna stations arranged on a 100 x 100 square grid, separated by about 300m. Each station consists of a small group of cross-polarized antennas residing just beneath the snow surface and facing downwards. They communicate with a central control hub by wireless links to generate global triggers.

We review recent application specific integrated circuits developed for high energy neutrino, gamma ray and cosmic ray detectors, which share constraints of the same kind. We compare various technical concepts used to fulfil similar requirements. We suggest some ways which could be followed in the near future to answer the needs of next generation experiments.

Astrophysical neutrinos at EeV energies promise to be an interesting source for astrophysics and particle physics. Detecting the predicted cosmogenic (Greisen-Zatsepin- Kusmin, "GZK") neutrinos at 10¹⁶ - 10²⁰ eV would test models of cosmic ray production at these energies and probe particle physics at ∼100 TeV center-of-mass energy. IceCube may be able to detect ∼10 GZK events per year with an extension including optical, radio, and acoustic receivers sparsely arrayed surrounding the optical core. Such a detector would feature crosscalibration with coincident events and would allow superior background rejection capability, energy and direction resolution, and confidence in discovered signals compared to single-method detectors. We present estimates of the neutrino effective volume for such a hybrid array both with the single-method sub-arrays independently and requiring combinations of sub-arrays to detect the same events. We also present ideas on hybrid event reconstruction and results from a proof-of-principle Monte Carlo test of a hybrid reconstruction algorithm.

The detection of extraterrestrial EHE neutrinos requires detection volumes at least one order of magnitude larger than currently constructed km3 optical neutrino detectors. In ice, it is anticipated that the absorption length for acoustic waves reaches up to to several kilometers. This makes ice an attractive host environment for a next generation acoustic neutrino detector. To measure the acoustic properties of ice at South Pole, a test setup has been developed, ready to be deployed in the 2006/07 summer season.

The acoustic detection method is a promising option for future neutrino telescopes operating in the ultra-high energy regime. It utilises the effect that a cascade evolving from a neutrino interaction generates a sound wave, and is applicable in different target materials like water, ice and salt. Described here are the developments in and the plans for the research on acoustic particle detection in water performed by the ANTARES group at the University of Erlangen within the framework of the ANTARES experiment in the Mediterranean Sea. A set of acoustic sensors will be integrated into this optical neutrino telescope to test acoustic particle detection methods and perform background studies.

We describe the beginnings of a multi-wavelength analysis of TeV blazars using observations from the WIYN 0.9m optical telescope, the VERITAS gamma-ray telescope, and the AMANDA/IceCube neutrino detector. Optical data were taken for Mrk 421, Mrk 501, and 1ES 1959+650 in coincidence with gamma-ray observations over a two-month period in Apr- June 2006. In the future we hope to use a statistical analysis of TeV flares in order to determine the significance of time-correlated neutrino detection with AMANDA/IceCube.

The high energy end of γ-ray source spectra might provide important clues regarding the nature of the processes involved in γ-ray emission. Several galactic sources with hard emission spectra extending up to more than 30 TeV have already been reported. Measurements around 100 TeV and above should be an important goal for the next generation of high energy γ-ray astronomy experiments. Here we present several techniques providing the required exposure (∼ 100 km² ⋅ h). We focus our study on three Imaging Atmospheric Cherenkov Technique (IACT) based approaches: low elevation observations, large field of view telescopes, and large telescope arrays. We comment on the advantages and disadvantages of each approach and report simulation based estimates of their energy ranges and sensitivities.

The Track Imaging Cerenkov Experiment (TrICE) aims for a ground-based measurement of high energy cosmic-ray composition using a novel technique. By separating the Cerenkov emission from the primary and secondary particles, nearly elemental charge resolution can be established. Here the status of the TrICE experiment is discussed.

VERITAS, the Very Energetic Radiation Imaging Telescope Array System, is a major new ground-based observatory for studying nonthermal astrophysics in the gamma-ray band above 100 GeV. VERITAS has operated a stereo pair of telescopes using a true array trigger at the Mt. Hopkins base camp site in southern Arizona since March, 2006. We report here on the status of certain key technical aspects of the project, including the optomechanical system and the trigger electronics.

The third EGRET catalog contains a large number of unidentified sources. Current data allows the intriguing possibility that some of these objects may represent a new class of yet undiscovered gamma-ray sources. By assuming that galaxies similar to the Milky Way host comparable populations of objects, we constrain the allowed Galactic abundance and distribution of various classes of gamma-ray sources using the EGRET data set. Furthermore, regardless of the nature of the unidentified sources, faint unresolved objects of the same class contribute to the observed diffuse gamma-ray background. We investigate the potential contribution of these unresolved sources to the extragalactic gamma-ray background.

We have derived a useful analytic approximation for determining the effect of intergalactic absorption on the γ-ray spectra of TeV blazars the energy range 0.2 TeV < E_γ < 2 TeV and the redshift range 0.05 < z < 0.4. In these ranges, the form of the absorption coeffcient τ (E_γ) is approximately logarithmic. The effect of this energy dependence is to steepen intrinsic source spectra such that a source with an approximate power-law spectral index Γ_s is converted to one with an observed spectral index Γ_o ≃ Γ_s + ΔΓ(z) where ΔΓ(z) is a linear function of z in the redshift range 0.05-0.4. We apply this approximation to the spectra of 7 TeV blazars.

Current neutrino detectors are approaching a sensitivity that allows one to detect Active Galactic Nuclei (AGN) in their high state. However, the expected signals might be too weak to result in a significant detection. One possibility to increase the detection chance is to focus the searches during states of high electromagnetic activity, especially in the very high energy (VHE) gamma-ray regime. In this context a good knowledge of the phenomenology of gamma-ray flux variability of the known VHE AGN is crucial. Here, we present our effort in archiving and combining VHE gamma-ray lightcurves and first results including a lightcurve of Mrk 421 spanning 15 years and the estimation of an average observed high state rate.

Through use of new algorithms for estimating γ-ray and cosmic ray primary energies of events in Milagro we determine the energy spectra of gamma rays from the Crab nebula and spectra of Milagro background triggers have been determined in the energy range 1 to 100 TeV. The measured spectra are compared with those measured by ACT techniques and direct measurements of cosmic ray spectra.

We show in this paper the analysis of the AMANDA-II data looking for events correlated with the giant flare observed in December 27th 2004 from the Soft Gamma-ray Repeater 1806-20. This flare was more than two orders of magnitude brighter than any previous flare of this kind and saturated the satellite gamma detectors that observed it. If a hard component of gamma-rays was present in the event, these would produce detectable rates of muons in underground detectors like AMANDA. Moreover, high-energy neutrinos could also have been emitted in quantities large enough to produce a signal in this detector. The unblinding of the data showed no signal, so upper limits were set both to the gamma-ray and the neutrino fluxes.

The next generation high energy neutrino and cosmic ray array IceCube/IceTop is under construction at the geographic South-Pole. Air showers with trajectories that pass through the surface array and near the deep strings trigger both components in coincidence. The ratio of the muon signal in the deep detectors to the shower signal on the surface is sensitive to the elemental composition of the primary cosmic radiation.

We present here a comparison of interaction models commonly used for simulating cosmic ray shower development in the atmosphere at energies greater than 1 TeV. The implementations of these models in CORSIKA and the FLUKA transport and interaction code are relevant for extensive air shower experiments, neutrino telescopes, and gamma-ray surfacebased detectors. We compare the pion, kaon, charmed meson and baryon energy fractions and the multiplicities at the first interaction stage of monoenergetic protons on nitrogen nuclei in the range 1 TeV-100 PeV. We also show comparisons in terms of Z-moments, a spectrumweighted multiplicity often used in the cosmic ray community. The transverse and longitudinal momentum distributions of the secondary muons produced in proton-nitrogen collisions are also shown.

During the last two austral summers, the first sensors of the IceCube neutrino observatory were deployed in the deep Antarctic ice, along with a surface array. We will present first results obtained using the IceCube detector, demonstrating that the performance is within the design requirements, and showing the ability to reconstruct tracks, cascades and synchronizing times in the entire array to within 3 ns.

A search for TeV to PeV muon neutrinos from unresolved sources was performed on AMANDA-II data collected between 2000 to 2003. The diffuse analysis sought to identify an extraterrestrial neutrino signal on top of the atmospheric muon and neutrino backgrounds. An upper limit of E²Φ_90%C.L. < 8.8 × 10⁻⁸ GeV cm⁻² s⁻¹ sr⁻¹ was placed on the diffuse flux of muon neutrinos with a dN/dE ∼ E⁻² spectrum for the energy range 15.8 TeV to 2.5 PeV. Limits were also placed on prompt and astrophysical neutrino models with other energy spectra.

The hadronic fireball model predicts a neutrino flux in the TeV to several PeV range simultaneous with the prompt photon emission of GRBs. The discovery of high energy neutrinos in coincidence with a gamma ray burst would help confirm the role of GRBs as accelerators of high energy cosmic rays. We summarize the methods employed by the AMANDA experiment in the search for neutrinos from GRBs and present results from several analyses.

The NEMO (NEutrino Mediterranean Observatory) Collaboration is constructing, 25 km E from Catania (Sicily) at 2000 m depth, an underwater test site to perform long-term tests of prototypes and new technologies for an underwater high energy neutrino detector in the Mediterranean Sea. In this framework the collaboration deployed and operated an experimental apparatus for on-line monitoring of deep-sea noise. The station is equipped with 4 hydrophones operational in the range 30 Hz - 40 kHz. This interval of frequencies matches the range suitable for acoustic detection of high energy neutrino-induced showers in water. Hydrophone signals are digitized underwater at 96 kHz sampling frequency and 24 bits resolution. A custom software was developed to record data on high resolution 4-channels PCM .le. Data are used to model underwater acoustic noise as a function of frequency and time, a mandatory parametre for future acoustic neutrino detectors. Results indicate that the average noise in the site is compatible with noise produced in condition of sea surface agitation (sea state.)

The PDF file lists the IceCube Collaboration.